Here are more questions about our favorite topic - fillets!

I tried a couple of things to fillet my strat model and had some success, but some issues too. Here are the questions...

1. can I specify a radius with more digits of precision than 2? I'm mapping to inches and the radius is 0.4375 in some cases. It shows up in the box as 0.44

2. I'm guessing that the G1, G2, G3 are different shapes with adjustable bulges. Is there a description somewhere about the differences? I think I used G1 for the main body outline.

3. here's what I tried to do.

a) I took my existing slab and trimmed off the top part with tight curves and then extruded and unioned it together

b) I then filleted the whole body at 0.44 and used the original cutting line to trim square

c) I filleted the desired edges on the small trimmed off piece to 0.125 and unioned it with the main body.

d) I trimmed off the armrest and body rest and then started to try and fillet those.

I had issues...


1. It look like some artifacts because the bottom fillet and armrest fillet ran into each other. I guess I need to adjust the trimming surface or reduce the fillet radius. Right? Also, should I stay circular or use one of the GX fillets.




2. I Knew I was going to get something like this using the technique I did, but is there an easy way to blend the small radius into the large radius?




3. This was strange. After I glued back the trimmed and filleted piece it didn't fit right. I thought the original curve attached to the straight part at this point and they were flush originally, but now it looks like the main part bulged out.




I guess I could have squared off the top or the model and then fillet edges separately, but I need to use multiple radiuses and still blend the 1/8" into the 7/16" fillets. Is this the preferred strategy?

I attached one of my versions of this model if anyone wants to play with it.

Thanks as always.

Hi Jeff, just a couple of the easy questions first:

> 1. can I specify a radius with more digits of precision
> than 2? I'm mapping to inches and the radius is 0.4375
> in some cases. It shows up in the box as 0.44

Yeah you can type in as many digits as you like - the 0.44 will be displayed when you go to run the Fillet command a second time and the edit field is showing you the value from the previous run. Numbers that are displayed in the UI like that use a setting for how many digits to display - you can adjust that under Options > General > Decimal display to make displayed numbers use more digits.

Maybe in the future I can tune this up so that it would remember that you typed in that number directly (rather than using the mouse to generate it by picking points for example) and display the same as what you typed in instead of rounding the display using the default display precision like it does now.

But anyway, if you up the display precision to use more decimal places for displaying numbers that would do the trick for now.


> 2. I'm guessing that the G1, G2, G3 are different shapes
> with adjustable bulges. Is there a description somewhere
> about the differences? I think I used G1 for the main body
> outline.

These refer to different types of continuity - G1 means tangent continuity, G2 means curvature continuity and G3 means continuity in the rate of change of curvature.

Each one of these gets kind of more complex and if you turn on surface control points in the blend you'll see that the higher continuity options require more control points to be created in the blend.

It's a rather difficult area to explain very clearly unfortunately, here is one previous attempt at explanation:
http://moi3d.com/forum/index.php?webtag=MOI&msg=290.2

- Michael

Hi Jeff,

> 1. It look like some artifacts because the bottom fillet and
> armrest fillet ran into each other. I guess I need to adjust the
> trimming surface or reduce the fillet radius. Right?

Yeah the filleter doesn't like it if there is not enough room for it to fit the fillet because there is a different edge that it would run into, so for example here:



There is not much room for a fillet to be placed around the upper edge there, before it would run into the bottom edge.

This limitation of the filleter not being able to cross over a neighboring edge, is probably the biggest general problem in the fillet engine - it's something that is handled better in the fillet engines in some other CAD programs.

But it looks like there was a partial result created, and it could be possible to salvage that by extracting the fillet surface and getting it into place by using the Trim command to manually cut back the surrounding areas to make the proper space for it.

What fillet radius do you want to have placed there?

Also there is another filleting option that is enabled if you are doing a fillet between 2 individual surfaces that are not joined to any other surface - that creates what is called a surface/surface fillet instead of an edge-based fillet. It can create fillet surfaces in cases where the edge-based one gets confused, so it can be helpful for some kinds of situations but it does not try to automatically handle corner juncture areas where multiple fillets may be running into each other like the edge based one.


> Also, should I stay circular or use one of the GX fillets.

That's up to you depending on what kind of a shape you want - the circular one makes a fillet surface that has an exact circular arc cross-section. That's often seen on mechanical shapes but it's not very organic because you seldom see an exact arc shape on a living creature for example. The Blend shapes make a more squishy type of surface that's kind of more organic in look. You can also tweak the bulgy-ness of the blend surface to make it kind of more flat or more like a ridge.

There is no automatic answer for which one is better, they generate a bit different shapes, so it depends on which kind of shape you like better.

A G2 blend will tend to make the fillet piece look less like a distinct separate part and be kind of more seamless with the surrounding geometry.

- Michael

> 2. I Knew I was going to get something like this using
> the technique I did, but is there an easy way to blend the
> small radius into the large radius?

Well, I guess you might have wanted something called a "variable radius fillet" in that case which is a type of fillet that has a radius that gradually changes from one particular radius to another radius value as the fillet travels along. MoI does not have that kind of filleting set up in it yet.

So you will probably want to create a similar kind of surface manually, something like this:

Start by selecting these faces here (there's also a little planar shelf like piece in there as well):



And then just hit Delete to remove them, leaving an empty hole there. Now you have some space to work with to fill in by constructing a surface that has the kind of transition that you want. You could draw in some guide rails and do a sweep, but actually the easiest is probably to use the Blend command. Select these 2 edges here:



And then run Construct > Blend - that will build a surface that connects smoothly between them, making this result:



Now the problem is the surrounding surfaces are not the right shape to match up with this new piece, so those have to be reconstructed as well.

Select these 2 adjacent faces now:



And delete those too, leaving a big hole above the blend and on the bottom:



These are both planar holes so they are easy to fill in though - to fill them in select the blend and the main guitar body and use the Edit > Join command to glue them together to be connected.

After you do that, you have 2 planar holes you want to fill in which the Construct > Planar command can do for you - just select the object and run Construct > Planar and it will create planar faces and join them in to make the guitar a solid again.

Let me know if you get stuck on any of these steps.

- Michael

Hi Jeff,

> 3. This was strange. After I glued back the trimmed and
> filleted piece it didn't fit right. I thought the original curve
> attached to the straight part at this point and they were
> flush originally, but now it looks like the main part bulged out.

Sorry, I'm having difficulty understanding this part - which is the bulged out piece? Can you circle it or something?

- Michael

Hello Michael,

FYI, I think I'm in your backyard. I just arrived in Redmond. Anyway on to filleting...

I'm always posting these when I'm 3/4 asleep so I may not be completely coherent.

The first image here shows how I need to fillet the top of the back of the body. I think I may change to squaring off the top and fillet edge by edge. Since the fillet engine can't change radii I was thinking of using a sweep or loft to do the areas that transition from 7/16" to 1/8".



The bulging comment was referring to the circled section. This used to be flush before I cut, filleted and glued back together. Now it looks like the main piece grew.



Good night.

Jeff

Hi Jeff,

> Since the fillet engine can't change radii I was thinking of
> using a sweep or loft to do the areas that transition from
> 7/16" to 1/8".

Yes, you'd need to do something along those lines to build a surface for that part.


> The bulging comment was referring to the circled section. This
> used to be flush before I cut, filleted and glued back together.
> Now it looks like the main piece grew.

Hmmm, yeah it looks like something was a little misaligned there, making that little shelf area.

It's hard to tell exactly what went wrong just looking at the final result here - if you possibly have some of the previous stages of the model that had the pieces you were cutting and gluing together, that would be where to look to see if some piece was not quite exactly aligned with some other piece being cut, making a little shelf like that.

It is possible to do some low level repair on things to fix problems like this, there is a tutorial on that kind of object repair techniques available here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=446.17

- Michael